A conventionally known variable valve operating device that is disclosed, for instance, by Japanese Patent Laid-open No. 2003-239712 mechanically changes the valve lift amount and valve timing in accordance with the operating state of an engine. For the variable valve operating device described in Japanese Patent Laid-open No. 2003-239712, a control arm is fastened to a control shaft that is positioned in parallel with a camshaft, and one end of a follower is mounted on the control arm and allowed to swing freely. Further, a swing cam is mounted on the control shaft and allowed to swing freely. A rocker arm is pressed against the surface of the swing cam. A first roller and a second roller are concentrically mounted on the follower so that these rollers can rotate independently of each other. The first roller is in contact with a valve cam on the camshaft, and the second roller is in contact with a contact surface that is formed on the side away from the cam surface of the swing cam.
When the control arm rotation position changes due to control shaft rotation while the above configuration is employed, the follower becomes displaced so as to change the distance between the control shaft and the contact between the swing cam and second roller. Consequently, the valve lift amount changes. Further, the circumferential position of the valve cam, which comes into contact with the first roller, changes in the same rotation position of the camshaft. This causes the valve timing to change also. In other words, the variable valve operating device described in Japanese Patent Laid-open No. 2003-239712 can simultaneously change the valve lift amount and valve timing when the rotation position of the control shaft is controlled by a motor.
Including the above-mentioned document, the applicant is aware of the following documents as a related art of the present invention.
[Patent Document 1]
Japanese Patent Laid-open No. 2003-239712
[Patent Document 2]
Japanese Patent Laid-open No. Hei7-63023
[Patent Document 3]
Japanese Patent Laid-open No. Hei6-74011
[Patent Document 4]
Japanese Patent Laid-open No. Hei6-17628
[Patent Document 5]
Japanese Patent Laid-open No. Hei11-36833